U.S. patent number 6,820,747 [Application Number 10/095,860] was granted by the patent office on 2004-11-23 for screen assembly.
This patent grant is currently assigned to Sedgman, LLC. Invention is credited to Daniel S. Placha, Larry A. Watters.
United States Patent |
6,820,747 |
Watters , et al. |
November 23, 2004 |
Screen assembly
Abstract
In a coal preparation plant which receives a raw coal feed and
separates the raw coal feed into clean coal feed and refuse feed
slurries using a media based separation process, an apparatus is
provided for use therein. The inventive apparatus simultaneously
processes the raw coal feed and clean coal feed and refuse feed
slurries, while occupying minimal floor space within the coal
preparation plant. The inventive apparatus includes a unitary
vibrating screen assembly having a length and a width, wherein the
width of the vibrating screen assembly is partitioned into three
screen sections extending the length of the vibrating screen
assembly. A deslime screen section receives the raw coal feed and
separates the raw coal feed into coarse and fine sized fractions as
the raw coal feed moves along the length of the deslime screen
section. A refuse screen section receives the refuse feed slurry
and removes separation media therefrom as the refuse feed slurry
moves along the length of the refuse screen section. Similarly, a
clean coal screen section receives the clean coal feed slurry and
removes separation media therefrom as the clean coal feed slurry
moves along the length of the clean coal screen section.
Inventors: |
Watters; Larry A. (McMurray,
PA), Placha; Daniel S. (Oakdale, PA) |
Assignee: |
Sedgman, LLC (Pittsburgh,
PA)
|
Family
ID: |
28038942 |
Appl.
No.: |
10/095,860 |
Filed: |
March 12, 2002 |
Current U.S.
Class: |
209/275;
209/277 |
Current CPC
Class: |
B07B
1/46 (20130101); B07B 1/4672 (20130101); B07B
2230/01 (20130101); B07B 2201/04 (20130101) |
Current International
Class: |
B07B
1/46 (20060101); B07B 001/00 () |
Field of
Search: |
;209/17,315,264,274,275,276,277,281,282,906 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Walsh; Donald P.
Assistant Examiner: Rodriguez; Joseph
Attorney, Agent or Firm: Buchanan Ingersoll, PC
Claims
We claim:
1. In a mineral preparation plant receiving a raw mineral feed and
separating the raw mineral feed into a clean mineral feed slurry
and a refuse feed slurry, an apparatus for simultaneously
processing the raw mineral feed and clean mineral and refuse feed
slurries, said apparatus comprising: a unitary screen assembly
having a length and width, wherein the width of the unitary screen
assembly is partitioned into three sections extending the length of
the unitary screen assembly and including: a deslime section
receiving the raw mineral feed and separating the raw mineral feed
into coarse and fine sized fractions as the raw mineral feed moves
along the length of the deslime section; a refuse section receiving
the refuse feed slurry including solid refuse particles and a
slurry of media and water and separating the solid refuse particles
from the slurry of media and water as the refuse feed slurry moves
along the length of the refuse section; and a clean mineral section
receiving the clean mineral feed slurry including solid clean
mineral particles and a slurry of media and water and separating
the solid clean mineral particles from the slurry of media and
water as the clean mineral feed slurry moves along the length of
the clean mineral section; a first feed supplying the raw mineral
feed to the deslime section; a second feed supplying the refuse
feed slurry to the refuse section; and a third feed supplying the
clean mineral feed slurry to the clean mineral section.
2. The apparatus of claim 1, wherein the deslime section includes a
first screen having a first mesh allowing the raw mineral feed
particles less than a first diameter to pass through, and a first
underpan receiving the raw mineral feed particles passing through
the first screen, the refuse section includes a second screen
having a second mesh screening the solid refuse particles greater
than a second diameter from the refuse feed slurry, and a second
underpan receiving the slurry of media and water passing through
the second screen, and the clean mineral section includes a third
screen having a third mesh screening the solid clean mineral
particles greater than a third diameter from the clean mineral
slurry, and a third underpan receiving the slurry of media and
water passing through the third screen.
3. The apparatus of claim 2, wherein the deslime section includes a
fourth screen between the first screen and underpan having a fourth
mesh allowing the raw mineral feed particles less than a fourth
diameter to pass through the fourth screen to the first underpan,
the fourth diameter being less than the first diameter, the refuse
section includes a fifth screen between the second screen and
underpan having a fifth mesh screening the solid refuse particles
greater than a fifth diameter passing through the second screen and
allowing the slurry of media and water to pass through to the
second underpan, the fifth diameter being less than the second
diameter, and the clean mineral second includes a sixth screen
between the third screen and underpan having a sixth mesh screening
the solid clean mineral particles greater than a sixth diameter
passing through the third screen and allowing the slurry of media
and water to pass through to the third underpan, the sixth diameter
being less than the third diameter.
4. The apparatus of claim 2, wherein the refuse and clean mineral
sections are adjacent one another, and wherein the second and third
underpans comprise a single underpan receiving the slurries of
media and water particles passing through the second and third
screens.
5. The apparatus of claim 1, wherein the mineral comprises coal,
and wherein the media comprises magnetite.
6. The apparatus of claim 1, further comprising first and second
partition members extending along the length of the unitary screen
assembly, the first partition member separating the deslime and
refuse sections, and the second partition member separating the
refuse and clean mineral sections.
7. The apparatus of claim 6, wherein the first and second partition
members extend vertically and substantially normal to the unitary
screen assembly.
8. The apparatus of claim 1, wherein the unitary screen assembly
comprises a banana screen.
9. In a mineral preparation plant receiving a raw mineral feed and
separating the raw mineral feed into a clean mineral feed slurry
and a refuse feed slurry, an apparatus for simultaneously
processing the raw mineral feed and clean mineral and refuse feed
slurries, said apparatus comprising: a unitary vibrating screen
assembly having a length and a width, the respective particles
moved along the unitary vibrating assembly screen length via
gravitational and/or vibrational forces, wherein the width of the
unitary vibrating screen assembly is partitioned into three
sections extending the length of the unitary vibrating screen
assembly and including: a first screen section receiving the raw
mineral feed and separating the raw mineral feed into coarse and
fine sized fractions as the raw mineral feed move along the length
of the first screen section; a second screen section receiving the
refuse feed slurry including solid refuse particles and a slurry of
media and water and separating the solid refuse particles from the
slurry of media and water as the refuse feed slurry moves along the
length of the second screen section; and a third screen section
receiving the clean mineral feed slurry including solid clean
mineral particles and a slurry of media and water and separating
the solid clean mineral particles from the slurry of media and
water as the clean mineral feed slurry moves along the length of
the third screen section; a first feed supplying the raw mineral
feed to the first screen section; a second feed supplying the
refuse feed slurry to the second screen section; and a third feed
supplying the clean mineral feed slurry to the third screen
section.
10. The apparatus of claim 9, wherein the first screen section
includes a first screen having a first mesh screening the raw
mineral feed particles greater than a first diameter, the screened
raw mineral feed particles on the first screen passing to a first
processing section of the mineral preparation plant, the second
screen section includes a second screen having a second mesh
screening the solid refuse particles greater than a second diameter
from the refuse feed slurry, the screened solid refuse particles on
the second screen passing to a refuse handling section of the
mineral preparation plant, and the third screen section includes a
third screen having a third mesh screening the solid clean mineral
particles greater than a third diameter from the clean mineral feed
slurry, the screened solid clean mineral particles on the third
screen passing to a clean mineral handling section of the mineral
preparation plant.
11. The apparatus of claim 10, wherein the first screen section
includes a fourth screen directly below the first screen and having
a fourth mesh screening the raw mineral feed particles greater than
a fourth diameter passing through the first, the fourth diameter
being less than the first diameter, the screened raw mineral feed
particles on the fourth screen passing to the first processing
section of the mineral preparation plant, the second screen section
includes a fifth screen directly below the second screen and having
a fifth mesh screening the solid refuse particles greater than a
fifth diameter passing through the second screen from the refuse
feed slurry, the fifth diameter being less than the second
diameter, the screened solid refuse particles on the fifth screen
passing to the refuse handling section of the mineral preparation
plant, and the third screen section includes a sixth screen
directly below the third screen and having a sixth mesh screening
the solid clean mineral particles greater than a sixth diameter
passing through the third screen from the clean mineral feed
slurry, the sixth diameter being less than the third diameter, the
screened solid clean mineral particles on the sixth screen passing
to the clean mineral handling section of the mineral preparation
plant.
12. The apparatus of claim 10, wherein the first screen section
includes a first underpan receiving the raw mineral feed particles
passing through the first screen, wherein the raw mineral feed
particles received by the first underpan are passed to a second
mineral processing section of the mineral preparation plant, the
second screen section includes a second underpan receiving the
slurry of media and water passing through the second screen, and
the third screen section includes a third underpan receiving the
slurry of media and water passing through the third screen.
13. The apparatus of claim 12, wherein the second and third
underpans comprise a single underpan receiving the slurries of
media and water passing through the second and third screens.
14. The apparatus of claim 12, wherein the second and third
underpans each include drain and rinse sections, and wherein said
apparatus further comprises at least one sprayer spraying rinse
water onto the second and third screens at the rinse sections of
their respective underpans to rinse off media adhering to the solid
refuse and clean mineral particles on the second and third screens,
respectively, wherein the rinse section of the second underpan
receives a slurry of rinse water and media passing through the
second screen, and wherein the rinse section of the third underpan
receives a slurry of rinse water and media passing through the
third screen.
15. The apparatus of claim 12, further comprising a water source
providing water onto the raw mineral feed on the first screen,
wherein the first underpan receives a slurry of water and fine
sized raw mineral feed particles passing through the first
screen.
16. The apparatus of claim 9, wherein the unitary vibrating screen
assembly comprises a banana screen having first and second
vertically extending partition members provided lengthwise along
the banana screen, the first partition member separating the first
and second screen sections, and the second partition member
separating the second and third screen sections.
17. The apparatus of claim 16, wherein the banana screen comprises
a double deck banana screen.
18. In a mineral preparation plant receiving a raw mineral feed and
separating the raw mineral feed into a clean mineral feed and a
refuse feed, an apparatus for simultaneously processing the raw
mineral, clean mineral and refuse feeds, said apparatus comprising:
a unitary banana screen assembly configured for simultaneous
processing of the raw mineral, clean mineral and refuse feeds, the
unitary banana screen comprising: a first screen deck having a
length and a width, the first screen deck including first and
second partition members extending the length of the first screen
deck and partitioning the first screen deck into first, second and
third screen sections for simultaneously processing the raw
mineral, refuse and clean mineral feeds, respectively; a first feed
supplying the raw mineral feed to the first screen section; a
second feed supplying the refuse feed slurry to the second screen
section; and a third feed supplying the clean mineral feed slurry
to the third screen section.
19. The improved apparatus of claim 18, wherein the unitary banana
screen further comprises: a second screen deck positioned
underneath the first screen deck and having a length and width
corresponding thereto, the second screen deck including third and
fourth partition members extending the length of the second screen
deck and partitioning the second screen deck into first, second and
third screen sections, corresponding to the first, second and third
screen sections of the first screen deck, for further
simultaneously processing the raw mineral, refuse and clean mineral
feeds, respectively.
20. The improved apparatus of claim 19, wherein the unitary banana
screen further comprises: a first underpan positioned underneath
the first screen section of the second screen deck for receiving a
portion of the raw mineral feed passing through the first screen
sections of the first and second screen decks; and a second
underpan positioned underneath the second and third screen sections
of the second screen deck for receiving portions or the refuse and
clean mineral feeds passing through the second and third screen
sections, respectively, of the first and second screen decks.
Description
FIELD OF THE INVENTION
The present invention is directed generally toward coal preparation
plants and, more particularly, toward an improved screen assembly
apparatus for use in coal preparation plants.
BACKGROUND OF THE INVENTION
Coal preparation plants separate organic and non-organic solid
particles by their specific gravities. The coal preparation plant
receives a feed of raw mined coal, and separates the raw mined coal
into clean coal and refuse. These plants typically utilize two
basic processing methods for separating raw coal from rock and
varying proportions of striated rock and coal from the higher
quality coal. The two processing methods include heavy media and
water based separation methods. Heavy media, utilizing a slurry of
media, e.g., water and magnetite or ferrosilicon, to separate the
coal from the refuse according to their specific gravity of dry
solids, is the most common separation process for larger size (Plus
1 mm-0.5 mm) particles. Whereas, water based separation processes
are more commonly used for the "cleaning" of the finer sized
particles, as that term is conventionally understood in the coal
processing art. One type of heavy media circuitry used in the coal
preparation plants includes a heavy media cyclone.
Coal preparation plants using heavy media cyclones operate with
three separate types of screens for coal processing, namely, a
deslime screen, a refuse screen and a clean coal screen. A common
screening assembly used in many coal preparation plants is today
known as a vibratory banana screen. The deslime screen receives the
raw coal feed particles and separates them into coarse and fine
sized fractions. The coarse or larger sized particles discharged
from the screen surface are directed to the heavy media separation
section of the coal preparation plant, while the finer sized
particles passing through the deslime screen are directed toward
the water based separation section of the coal preparation
plant.
The separate clean coal and refuse screens receive the clean coal
and refuse particles, respectively produced by the heavy media
separating section. While on the clean coal and refuse screens, the
clean coal and refuse particles are rinsed with water, and the
finer particles and water passing through the respective screens
are recirculated through the coal preparation plant. Rinsing the
clean coal and refuse particles is primarily done to recover the
particles of media, such as magnetite, remaining thereon as a
result of the coal/refuse separation process, as magnetite can be
quite expensive.
Often, the deslime, clean coal and refuse screens are located in
different areas of the coal preparation plant and/or on different
floors. In addition to being an inefficient use of space and
increasing the cost of the coal preparation plant, this situation
creates a burden for the plant operator wishing to view the feeds
and discharges of raw coal, clean coal and refuse screens.
The present invention is directed toward overcoming one or more of
the above-mentioned problems.
SUMMARY OF THE INVENTION
In a coal preparation plant which receives a raw coal feed and
separates the raw coal feed into clean coal and refuse particles
using a media based separation process, an apparatus is provided
for use therein. The inventive apparatus simultaneously processes
the raw coal feed, clean coal and refuse particles, while occupying
minimal floor space within the coal preparation plant. The
inventive apparatus includes a unitary vibrating screen assembly
having a length and a width, wherein the width of the vibrating
screen assembly is partitioned into three screen sections extending
the length of the vibrating screen assembly. A deslime screen
section receives the raw coal feed particles and separates the raw
coal feed particles into coarse and fine sized fractions as the raw
coal feed particles move along the length of the deslime screen
section. Two separate drain and rinse sections of the screen
receive the refuse and clean coal particles, respectively, and
remove media remaining on these particles as they move along the
length of the respective screen section.
Typically, the various feed particles are moved along the length of
the unitary vibrating screen assembly via gravitational and/or
vibrating forces. The unitary vibrating screen assembly may be of
single or double deck construction, as those terms are
conventionally understood in the coal processing art.
In one form, the deslime screen section includes an underpan
receiving the fine sized raw coal feed particles passing through
the deslime screen section. The fine sized raw coal feed particles
received by this underpan are passed to a fine coal, or water
based, processing section of the coal preparation plant. The two
separate drain and rinse sections each include a separate underpan
receiving the media particles which pass through the respective
screen section and are recovered from the refuse and clean coal
particles. The recovered media particles received by these
underpans are recirculated through and/or further processed by the
coal preparation plant.
The underpans of the two separate drain and rinse sections may be
combined into a single underpan receiving the recovered media
particles passing through the screen sections, respectively, for
recirculation through and/or further processing by the coal
preparation plant.
Sprayers are provided for adding water onto the deslime screen
section, and the two separate drain and rinse screen sections to
rinse the raw coal feed, refuse and clean coal particles,
respectively. Water is used to aid in particle separation in the
deslime screen section and also to remove media from the refuse and
clean coal particles in the two drain and rinse screen sections,
respectively.
In another form, partition members are provided lengthwise along
the unitary vibrating screen assembly extending vertically
therefrom to partition the unitary vibrating screen assembly into
the deslime and the two separate drain and rinse screen
sections.
In a preferred form, the inventive unitary vibrating screen
assembly includes a multislope "banana" screen of either a single
or double deck configuration.
It is an object of the present invention to: provide an improved
screen assembly in a coal preparation plant occupying minimal
space; and to provide an improved screen assembly for
simultaneously processing raw coal feed, refuse feed and clean coal
feed particles.
Other objects, aspects and advantages of the present invention can
be obtained from a study of the specification, the drawings, and
the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a screen assembly according to the
present invention;
FIG. 2 is a block diagram of a coal preparation plant incorporating
the inventive screen assembly;
FIG. 3 is an exploded perspective view of the inventive screen
assembly with partition members removed;
FIG. 4 is a side view a raw coal deslime section of the inventive
screen assembly;
FIG. 5 is a side view of a refuse section of the inventive screen
assembly; and
FIG. 6 is a side view of a clean coal section of the inventive
screen assembly.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIGS. 1-2, the inventive screen assembly 10 is shown
incorporated for use within a coal preparation plant 12. The coal
preparation plant 12 typically receives a raw coal feed 14 and
separates the raw coal feed 14 into clean coal 16 and refuse 18
particles. The inventive screen assembly 10 includes a unitary
screen assembly for simultaneously processing the raw coal feed 14,
clean coal 16 and refuse 18 particles. The screen assembly 10 has a
length "l" and a width "w" and is partitioned into deslime 20,
refuse 22 and clean coal 24 screen sections extending lengthwise,
with each section receiving and processing a different type of feed
particle.
The deslime screen section 20 includes top 26 and bottom 28 deck
screens. The top screen 26 includes a mesh which is larger than the
mesh of the bottom screen 28. The bottom screen 28 is disposed
directly below the top screen 26, and as the raw coal feed 14 is
passed across the length of the deslime screen section 20, the top
26 and bottom 28 screens screen the coarse raw coal feed particles
from the finer sized particles which fall through the screens 26
and 28 and into an underpan 30 disposed below the top 26 and bottom
28 screens. As a result of the larger mesh of the top screen 26,
the coarse raw coal feed particles 14 screened by the top screen 26
are of a larger diameter than those screened by the bottom screen
28.
The refuse screen section 22 also includes top 32 and bottom 34
deck screens, with the bottom screen 34 disposed below the top
screen 32. The top screen 32 has a mesh which is larger than the
mesh of the bottom screen 34. As the refuse particles 18 are passed
across the length of the refuse screen section 22, the solid refuse
particles are screened by the top 32 and bottom 34 screens, with
the finer sized particles of refuse (misplaced refuse fines)
passing through the screens 32 and 34 to an underpan 36 disposed
below the top 32 and bottom 34 screens. As a result of the larger
mesh of the top screen 32, the solid refuse particles 18 screened
by the top screen 32 are of a larger diameter than those screened
by the bottom screen 34.
Similarly, the clean coal screen section 24 includes top 38 and
bottom 40 deck screens, with the bottom screen 40 disposed below
the top screen 38. The top screen 38 has a mesh which is larger
than the mesh of the bottom screen 40. As the clean coal particles
16 are passed across the length of the clean coal screen section
24, the solid clean coal particles are screened by the top 38 and
bottom 40 screens, with the finer sized clean coal particles
(misplaced clean coal fines) passing through the screens 38 and 40
and into an underpan 42 disposed below the top 38 and bottom 40
screens. As a result of the larger mesh of the top screen 38, the
solid clean coal feed particles 16 screened by the top screen 38
are of a larger diameter than those screened by the bottom screen
40.
As shown in FIG. 1, each of the screens 26, 28, 32, 34, 38 and 40
are sloped such that the inventive screen assembly type is of the
type conventionally known as a banana screen. The top screens 26,
32 and 38 together constitute a first screen deck, while the bottom
screens 28, 34 and 40 together constitute a second screen deck.
A first partition member 44 separates the deslime 20 and refuse 22
screen sections. Similarly, a second partition member 46 separates
the refuse 22 and clean coal 24 screen sections. The first 44 and
second 46 partition members extend vertically from, and
substantially normal to, the top screens 26, 32 and 38. Similarly,
third 48 and fourth 50 partition members extend vertically from the
bottom screens 28, 34 and 40 up to the top screens 26, 32 and 38
and partition the bottom screens 28, 34 and 40 into the deslime 20,
refuse 22 and clean coal 24 screen sections, respectively.
Specifically, the third partition member 48 separates the deslime
screen section 20 from the refuse screen section 22, while the
fourth partition member 50 separates the refuse screen section 22
from the clean coal screen section 24. Typically, the partition
members 44, 46, 48 and 50 will be bolted to the frame (not shown)
of the screen assembly 10.
As shown in FIG. 2, the feed particles 14, 16 and 18 are provided
at a first, or input, end 51 of the screen assembly 10, which is
elevationally higher than a second, or output, end 52 of the screen
assembly 10. The feed particles 14, 16 and 18 are moved along the
length of the screen assembly 10 via gravitational forces acting
thereon. To aid in particle separation through the screens, and
also to help move the particles along the screens, the screens of
the screen assembly 10 are conventionally vibrated using a standard
vibration device 53 (see FIGS. 4-6).
As shown in FIG. 2, the coarse raw coal feed particles 14 screened
by the top 26 and bottom 28 screens are fed to a first processing
section 54 of the coal preparation plant 12. The processing section
54 utilizes conventional coal processing techniques to develop the
clean coal 16 and the refuse 18 particles. Typically, these
techniques will include heavy media separation methods. The finer
sized raw coal feed particles 14 falling to the underpan 30 are fed
to a second processing section 55 which conventionally processes
those finer sized coal particles, typically using water based
separation methods.
The solid refuse particles 18 screened by the top 32 and bottom 34
screens are fed to a conventional refuse handling section 56 of the
coal preparation plant 12. Similarly, the solid clean coal
particles 16 screened by the top 38 and bottom 40 screens are fed
to a conventional coal clean handling section 58 of the coal
preparation plant 12. Each of the finer sized refuse particles 18
and the finer sized clean coal particles 16 which are received in
the underpans 36 and 42, respectively, are fed to both the first
processing section 54 and the second processing section 55 for
recirculation through and/or further processing by the coal
preparation plant 12.
As shown in FIGS. 3-6, each of the screen sections 20, 22 and 24
includes sprayers 60 connected by valves 62 to a water source 64.
As the respective feed particles 14, 16 and 18 move along the
lengths of the respective screen sections 20, 22 and 24, they are
sprayed with water. With regard to the deslime screen section 20,
water is typically applied on the raw coal feed 14 to aid in
separating the finer sized raw coal particles from the coarse raw
coal particles. The water and finer sized raw feed particles which
pass through the top 26 and bottom 28 screens and into the underpan
30 are fed to the second processing section 55 via conduit 66 The
coarse raw coal feed particles screened by the top 26 and bottom 28
screens are fed to the first processing section 54 via conduit
68.
With respect to the refuse 22 and clean coal 24 screen sections,
rinsing the particles with water is done for a different reason.
Typically, magnetite is used as the media by the first processing
section 54 for separating the clean coal from the refuse. The first
processing section 54 produces the clean coal 16 and refuse 18
particles as slurries of solid clean coal/refuse, misplaced clean
coal/refuse fines, magnetite and water. Rinsing the solid refuse
and clean coal particles passing across the refuse 22 and clean
coal 24 screen sections, respectively, is done primarily to recover
the magnetite particles for recirculation through and/or further
processing by the coal preparation plant 12.
The underpan 36 of the refuse screen section 22 is divided into a
drain section 66 generally nearer the input end 51 and a rinse
section 68 extending from the drain section 66 to the output end
52. Since the refuse feed 18 is received at the refuse screen
section as a slurry of solid refuse, misplaced refuse fines,
magnetite and water, the majority of the magnetite will be
recovered from the refuse feed 18 in the drain section 66 of the
underpan 36, as it will simply pass through the screens 32 and 34.
However, the solid refuse particles screened by the screens 32 and
34 will have particles of magnetite adhering thereon. To recover
this magnetite, the sprayers 60 are positioned to apply water to
the screened solid refuse particles at the rinse section 68 of the
underpan 36. The magnetite and misplaced refuse fines rinsed off of
the screened refuse particles by the sprayers 60 are received in
the rinse section 68. The slurry of water, magnetite and misplaced
refuse fines from the drain section 66 is fed mainly to the first
processing section 54, with a portion fed to the second processing
section 55. The rinse section 68 of the underpan 36 will typically
include less magnetite, and the slurry of water, magnetite and
misplaced refuse fines from the rinse section 68 is fed to the
second processing section 55. The solid refuse particles 18
screened by the top 32 and bottom 34 screens are conventionally fed
to the refuse handling section 56 via conduit 70.
Similarly, the underpan 42 of the clean coal screen section 24 is
divided into a drain section 72 generally nearer the input end 51
and a rinse section 74 extending from the drain section 72 to the
output end 52. Since the clean coal 16 particles are received at
the clean coal screen section as a slurry of solid clean coal,
misplaced clean coal fines, magnetite and water, the majority of
the magnetite will be recovered from the clean coal particles 16 in
the drain section 72 of the underpan 42, as it will simply pass
through the screens 38 and 40. However, the solid clean coal
particles screened by the screen 38 and 40 will have particles of
magnetite adhering thereon. To recover this magnetite, the sprayers
60 are positioned to apply water to the screened solid clean coal
particles at the rinse section 74 of the underpan 42. The magnetite
and misplaced clean coal fines rinsed off of the screened clean
coal particles by the sprayers 60 are received in the rinse section
74. The slurry of water, magnetite and misplaced clean coal fines
from the drain section 72 is fed mainly to the first processing
section 54, with a portion fed to the second processing section 55.
The rinse section 74 of the underpan 42 will typically include less
magnetite, and the slurry of water, magnetite and misplaced clean
coal fines from the rinse section 74 is fed to the second
processing section 55. The solid clean coal particles 16 screened
by the top 38 and bottom 40 screens are conventionally fed to the
clean coal handling section 58 via conduit 76.
The above-described screen assembly 10 has the advantage that only
one screen assembly is needed for processing all three different
types of feed particles. Not only does this decrease costs and save
space in the preparation plant, but a plant operator can view the
screen assembly 10 and immediately observe the ratio of clean coal
to refuse that is present in the incoming raw coal being processed.
Since it is anticipated that the clean coal slurry 16 will be
greater than the refuse slurry 18, the clean coal screen section 24
will be wider than the refuse screen section 22 to accommodate a
higher volume. Using a 12'.times.20' (w.times.l) banana screen, it
is presently suggested that a partitioning of 5' for the deslime
section 20, 2' for the refuse section 22, and 5' for the clean coal
section 24 be implemented. However, other screen sizes,
partitioning widths, and relative feed locations are
contemplated.
Additionally, since the underpans 36 and 42 of the refuse 22 and
clean coal 24 screen sections, respectively, are similar in
construction with the recovered materials received therein passed
to the same sections within the coal preparation plant 12, the
underpans 36 and 42 may be replaced with a single underpan 76 (see
FIG. 2) underneath the screens of the refuse 22 and clean coal 24
screen sections.
While the present invention has been described with particular
reference to the drawings, it should be understood that various
modifications could be made without departing from the spirit and
scope of the present invention. For instance while the inventive
screen assembly 10 has been described herein as a double deck
banana screen, a single deck banana screen, eliminating the bottom
screens, may be utilized without departing from the spirit and
scope of the present invention. Further, screens other than banana
screens are contemplated and may be additionally implemented. Still
further, while the inventive screen assembly 10 has been shown and
described herein as used in a coal preparation plant 12, the
inventive screen assembly 10 may be utilized in preparation plants
for ore and minerals other than coal, using separation media other
than magnetite, without departing from the spirit and scope of the
present invention.
* * * * *